Now, this code does not currently work because the [GetKey()] step returns undefined, which is because KEY_UP, DOWN, etc. are actually numerical constants, and I can't seem to break them down within the object creation to do something like convert KEY_UP to 84, nor can I seem to get the value from GetKey() as its word form. I'm a bit stumped as to what to do here that would still result in legible code while also having equivalent functionality.

It's worth noting that this would have been possible if Sphere supported ES6 using computed property names, in which case you could just wrap KEY_UP etc. constants in brackets. Alas, ES6+ support still looks like it's a ways off for Duktape.